In recent years, use of a virtual computer environment has been increasing in a large scale data center. In the virtual computer environment, a software-defined network (SDN) that controls network equipment by software is constructed. In a virtual local area network (VLAN) constructed based on the SDN, in order to avoid a problem of insufficiency in section resource of network apparatuses or a problem of complexity in setting of network equipment, an overlay network technique for constructing an edge overlay is used.
As the edge overlay network technique, tunneling techniques such as a virtual extensible local area network (VXLAN) and a network virtualization using generic routing encapsulation (NVGRE) are known (NPLs 1 and 2). In these techniques, communication of a virtual network constructed in a virtual computer is encapsulated, and the communication is caused to flow in a basic network (Substrate Network or physical network) including network equipment configuring the virtual computer environment. In these tunneling techniques, section resource of the virtual network can be virtually increased by adding a virtual network ID (Identifier) upon encapsulating. Moreover, in these tunneling techniques, by using communication in the basic network, a load of setting for the network equipment is reduced.
However, these tunneling techniques do not define processing contents regarding a broadcast, a multicast, and an Unknown unicast in detail, but merely state the use of the IP (Internet Protocol) multicast technique of a basic network. An IP multicast address is sometimes shared, but is normally configured for each virtual network ID. Therefore, a multicast is delivered to the entire region of a network of the constructed virtual computer environment, i.e. the virtual network as an object (See “4.2. Broadcast Communication and Mapping to Multicast” of NPL 1 and “4.1. Broadcast and Multicast Traffic” of NPL 2).
Moreover, PTL 1 discloses a switch which is applied to a technique for encapsulating a packet by a header referred to as a TRILL (Transparent Interconnection of Lots of Links) header. The switch disclosed in PTL 1 is provided with a means for determining an internal multicast group identifier based on a source address, a multicast address, and a multicast tree identifier field, associated with a multicast packet. Moreover, this switch is provided with a means for transferring the multicast packet based on the internal multicast group identifier.
Furthermore, NPL 3 describes a network control technique referred to as OpenFlow. Using OpenFlow allows an OpenFlow switch to function as a TEP (Tunnel End Point) device of a tunneling technique.